Fix whitespace on login link/greeting.

The whitespace on the login button doesn't match that of the other navigation items, this feels a bit odd.
before:
![Screen Shot 2013-04-16 at 12 02 16](https://f.cloud.github.com/assets/150374/385286/c4bb6d42-a67c-11e2-8a64-b733059eab6a.png)
after:
![Screen Shot 2013-04-16 at 12 02 52](https://f.cloud.github.com/assets/150374/385288/d64c0d46-a67c-11e2-84f9-f09dcd925f4f.png)